Field of the Invention
This invention relates to airborne fire fighting suppression systems. In particular, the invention relates to an improved system for dispersing pressurized fire-extinguishing materials from an airborne fire fighting platform.
Description of Related Art
Aircraft are commonly employed for the aerial dispersion of liquid and/or solid materials such as fire retardant or fire extinguishing materials, oil dispersant materials, bio-remediation materials, fertilizer materials, herbicide materials, defoliant materials, pesticide materials, etc., over a target. Many vintage aircraft are converted for aerial dispersion of materials by the permanent installation of material dispersion equipment.
Modular aerial spraying systems have also been developed for use in conversion of cargo aircraft for aerial spraying purposes. Known as Modular Airborne Fire Fighting Systems (“MAFFS”) or advanced modular airborne fire fighting system, these systems employ portable pressurized tanks, which are loaded onto cargo aircraft, for instance C-130 aircraft, through the lowered rear cargo ramp of the aircraft.
Various fixed and rotary wing aircraft such as the Douglas DC-6 and DC-4, Lockheed Martin P-2 Neptune and P-3 Orion, and the Sikorsky UH-60L/S-70A Black Hawk helicopter and other types of fixed and rotary wing aircraft, have in the past been extensively modified to undertake airborne fire fighting operations. Typically, modifications to the airframe are made to accommodate the weight of, and loads resulting from the dispersal of high volume water and foam retardant fluid. These aircraft are referred to as air tankers. Their combined water and retardant delivery capacity, as well as the delivery dispersal pattern of the water on the ground, determine if the aircraft qualifies for one of several air tanker ratings, which are certified by the Interagency Air Tanker Board (IAB).
Among the many methodologies developed over years of aerial wildland fire fighting, is the constant flow retardant delivery tank system, which uses a pair of doors that open gradually to permit progressive release of the retardant mixture from within an air tanker's fluid reservoir. This constant flow water bombing methodology can counteract the forward motion of the aircraft at various speeds while maintaining an even, well grouped, user programmable, retardant dispersal pattern on the ground.
One variant of such a system was disclosed by MacDonald and Neuwirth, in U.S. Pat. No. 4,936,389, which issued on Jun. 26, 1990, entitled “Fluid Dispenser for an Aircraft”. MacDonald discloses a system wherein a head sensor determines the level of retardant in the aircraft retardant tank and dynamically controls the aperture of the drop doors to counter aircraft forward velocity to achieve a consistent dispersal pattern. A similar constant flow system, which calculates the remaining amount of fluid within a tank relative to aircraft ground speed to achieve controlled retardant discharge is disclosed by Foy and Uglum in U.S. Pat. No. 5,320,185, which issued on Jun. 15, 1994, entitled “Aircraft Fluid Drop System” and also Foy and Uglum in U.S. Pat. No. 5,451,016, which issued on Sep. 19, 1995, which was also entitled “Aircraft Fluid Drop System”.
Another methodology used to achieve constant flow rates is disclosed by Trotter and Woods in U.S. Pat. No. 5,279,481, which issued on Jan. 18, 1994, entitled “Airborne Liquid Spreading System”. In the disclosed system, the differential pressure across the drop doors between internal tank pressure and external ambient pressure is determined by a sensor which then relays signals to a controller that varies the aperture of the doors to maintain a constant flow rate during the drop sequence.
U.S. Pat. No. 7,165,627, entitled “Portable Airborne Firefighting and Sensing System”, discloses a fire fighting apparatus adapted for use in a host aircraft comprising a fuselage. The fire fighting apparatus includes a pressurizeable retardant tank disposed in the interior of the host aircraft, the retardant tank being capable of roll-on and roll-off installation, and utilizes an ejection tube in fluid communication with the retardant tank. Various sensors are disclosed to effect user-discernable data for directing retardant delivery.
A typical mobile air dispersal system consists of a series of pressurized fire retardant tanks, with a total capacity of 2,700 gallons and associated equipment, which is palletized and carried in the aircraft's cargo bay. In addition to the retardant tanks, each module contains a pressure tank where compressed air is stored at 1,200 psi. The control module includes the master control panel, the loadmaster's seat, and discharge valves. An air compressor module provides air pressure for charging the system; it stays at the air tanker base during air operations and is used to recharge the system between runs. Each unit weighs about 11,000 pounds, with a load capacity of 2,700 gallons. They can be installed in any C-130 equipped with the USAF 463L cargo-handling system.
All the aforementioned constant flow methodologies have certain limitations and deficiencies, most notably, the inability to precisely control the rate of the dispersal of the liquid load.
Accordingly, there is a continuing, unaddressed need for an improved firefighting apparatus capable of controlled and precise delivery of pressurized retardant.